Plastic zippers and method of making the same



Dec. 13, 1966 J. E. BURBANK 3,290,747

PLASTIC ZIPPERS AND METHOD OF MAKING THE SAME 2 Sheets-Sheet 1 Filed Feb. 18, 1965 Dec. 13, 1966 J. E. BURBANK 3,290,747

PLASTIC ZIPPERS AND METHOD OF MAKING THE SAME Filed Feb. 18, 1965 2 SheetsSheet 2 M A KN A I l I l l l/m United States PatentO 3,290,747 PLASTIC ZIPPERS AND METHOD OF MAKING THE SAME John E. Burbank, Middlebury, Conn., assignor to Scovill Manufacturing Company, Waterbury, Conn., a corporation of Connecticut I Filed Feb. 18, 1965, Ser. No. 433,598 6 Claims. (Cl. 24-20516) This invention is an improvement in plastic zipper fasteners of the continuous filament'type and an improved method of making the same.

In the manufacture of zippers of the plastic filament type, considerable difliculty has been experienced in obtaining satisfactory element-free tape end extensions which are desired for the attachment of stop elements and for anchoring the end of the zipper in place.

Previous methods involve the sewing of a continuous filament, after it has been formed into a coil or other shape to provide a series of loops by a continuous. line of stitching and then later cutting outpart of the filament. In this way, theend of the coil is not firmly held or bound to the tape. Even in cases where a cord extends longitudinally throughout the coil and a portion of the coil cut away to provide an-element-free extension or gap, the result is not entirely satisfactory. The stitching, even if not damaged, will-be comparatively loose because the threads would have to be long enough to extend over the coil portions which had to be cut away. Thus, when the coil is removed, the stitching is not firm or tight. The result is that neither the cord nor the end of the filament are bound firmly in place. Since the cord is relatively loose, it may slide in the coil at the ends.

According to my improved method, the coil with its enclosed cord, is provided with the gaps before the sewing operation. In this step, only the coil is removed, leaving the cord continuous and this serves to assist in feeding the stringer into the sewing machine. Furthermore, the scrap parts of the coil are more easily removed at this stage than in the old practice after the coil had been sewn to the tape.

In the sewing step, as soon as the needles come to the element-free portion of the tape and cord, they will bind the end of the coil and cord in the element-free portion tightly together because the same tensions will apply to the threads. The sewing operation preferably employs a plurality of threads so as to get ample covering of the coil and this, of course, tends to anchor the filament ends and cord even more firmly in the element-free portion.

In the accompanying drawing, I have shown for the purposes of illustration, one embodiment which the invention may assume in practice. In the drawings:

FIG. 1 is a diagrammatic view in perspective, illustrating the steps in my improved method of making fastener stringers;

FIG. 2 is a cross-section at the element-cutting station at the beginning of the cutting stroke;

FIG. 3 is a similar section with the cutting tool engaged in the fastener element;

FIG. 4 is also a cross-section at the cutting station, showing the completion of the cutting step;

FIG. 5 is a longitudinal vertical section on line 55 of FIG. 2;

FIG. 6 is an enlarged plan view of a portion of a continuous stringer, including an element-free gap;

FIG. 7 is a side view of the same stringer;

FIG. 8 is a cross-section on line 8-8 of FIG. 7; and

FIG. 9 is a front view illustrating a completed Zipper stringer length with element-free extensions at both ends.

As seen in FIG. 1, the coiled plastic filament 10 with its enclosed cord 11, is guided in a groove 12 of the table top 13. In this condition, it comes to the cutting station U 3,290,747 Patented Dec. 13, 1966 under the cutting tool, generally designated 14. This tool has on its front side preferably two cutting edges 15 and 16 between the prongs 17, and these prongs serve to line up the elements with the cutting edges when they penetrate between the convolutions of the coil.

In FIG. 3, on the down stroke of the cutting tool, the cutting edges have already severed the top sections of the coil and are ready to engage the bottom sections. At the completion of the operation, the head portions of the elements fall out as scrap, as indicated at 18 in FIG. 4, through a hole 19 in the table top. At the same time, a wedge-like projection 20 mounted on the cutting tool behind the cutting edges 15 and 16, enters in the in side portions of the cut coil and pushes it away as scrap, as indicated by the numerals 21 in FIG. 1; A transverse groove 22 may be formed at the table top 13 to convey these scrap pieces away.

After the required number of strokes to provide a desired length of gap G, the operation of the cutting tool 14 is temporarily halted while the cord and coil combination is fed to the sewing station. Between the cutting station and sewing station, the tape T is fed under a roller 23 into overlying relation with the coil 10. At the sewing station, the two needles 24 operate continuously to sew together the coil tape and cord with a continuous double line of stitching 25. The cord and coil assembly is advanced along the groove 12- by means of a feed wheel 26 actuated in a step-by-step manner. Between the cutting station and the sewing station, the cord which fits rather snugly inside the coil, serves to carry and support in proper position the portions of coil adjacent the gap G. Another feed wheel 27 operates in unison with the feed wheel 26 to assist in feeding the coil and cord assembly with the proper timing to the setting station. Finally, the finished product is conveyed away from the machine by a pair of rollers 28.

The important result accomplished by this improved method is a definitely better product, as best seen in the larger scale views of FIGS. 6-7-8. In addition to the needle threads 25 already mentioned, the sewing machine interlocks these threads with a third thread 29 which extends over the convolutions of the coil, and over the cord 11 where the coil assembly is cut away. In stitching through the gap, the threads will remain under the same tension and firmly tie the cord to the tape. The needle threads 25 will be closer to the cord than indicated in the diagrammatic view of FIG. 6, but in any case, the threads crossing over the cord will bind the cord securely to the tape. Also, these threads will anchor the cut coil ends, one of which is indicated at 30 and the other at 31.

The resulting finished product, as seen in FIG. 9, has the length of coil corresponding to the desired length of the finished zipper and the upper and lower element-free extensions 32 and 33, respectively. The cord cannot slide in the coil at either end because of the improved anchorage resulting from the method above described. There is, for the first time, a real continuity of union of the coil, cord and tape throughout the length of the stringer. The cut ends of the coil are held tightly, which was not the case with the old practice where the stitching at these points was left loose after the removal of the scrap pieces of coil.

Another advantage is that there is provided a firm and strong anchorage for stop elements, and this is especially advantageous in zippers of the separable bottom end type. In the latter case, the firm cord and tape combination provides a good support for the tubes or pins commonly employed in separable bottom ends.

While I have shown the stringer in FIG. 9 as having element-free extensions at both ends, it may be desirable in some uses of the zipper, to cut the cord and tape very 3 :lose to, or at one end of the gap, leaving only an elenent-free extension at one end.

What I claim is:

1. A zipper fastener stringer comprising a length of ape, a continuous plastic filament along the edge of said Lape, said filament being formed into a series of loops, :ach loop providing a fastener element, a cord extending .ongitudinally through said loops and overlying the edge portion of said tape, said tape and cord being longer than ;aid series of loops to provide an element-free extension at said tape and cord, and a continuous line of stitching which holds together said series of loops, cord and tape, ;aid line of stitching extending through said element-free :xtension where it tightly binds the cord directly to the :ape.

2. A zipper fastener stringer comprising a length of :ape, a plastic filament coil along the edge of said tape providing a series of fastener element loops, a cord ex- ;ending longitudinally through said loops and overlying the edge portion of said tape, said coil being shorter than the tape and cord so as to provide an element-free extension on at least one end of the stringer and a continuous line of stitching extending throughout the length of the stringer, said stitching extending over the convolutions of said coils, between the coils in the region of said cord and also through the tape, said line of stitching in the element-free portion having substantially the same tension as in the coil portion whereby the end of the coil and cord are bound tightly directly to the tape.

3. A zipper fastener stringer as defined in claim 2, wherein said continuous stitching comprises a plurality of threads arranged side by side and interlocked together over the cord in the element-free portions of the stringer.

4. A method of making zipper fastener stringers comprising feeding a continuous coil filament and a cord surrounded thereby, cutting gaps in the coil while leaving the cord intact and then sewing said coil and cord to a continuous tape by a continuous line of stitching which is maintained under the same tension through the gaps whereby the end portions of the coil and the cord in the gaps are anchored firmly to the tape.

5. The method defined in claim 4 wherein said line of stitching comprises a plurality of threads side by side at least one of which is closely adjacent each side of the cord and wherein said plural threads are interlocked together over the cord.

6. The method defined in claim 4 wherein the cord prior to sewing fits in the coil snugly enough so that it can assist in carrying the leading end of the cut coil toward the sewing machine.

References Cited by the Examiner UNITED STATES PATENTS 3,190,779 6/1965 Porepp 29408 X 3,245,136 4/1966 Taylor 29408 X 3,249,976 5/1966 Burbank 24205.16 X

FOREIGN PATENTS 977,842 12/ 1964 Great Britain.

BERNARD A. GELAK, Primary Examiner. 

1. A ZIPPER FASTENER STRINGER COMPRISING A LENGTH OF TAPE, A CONTINUOUS PLASTIC FILAMENT ALONG THE EDGE OF SAID TAPE, SAID FILAMENT BEING FORMED INTO A SERIES OF LOOPS, EACH LOOP PROVIDING A FASTENER ELEMENT, A CORD EXTENDING LONGITUDINALLY THROUGH SAID LOOPS AND OVERLYING THE EDGE PORTION OF SAID TAPE, SAID TAPE AND CORD BEING LONGER THAN SAID SERIES OF LOOPS TO PROVIDE AN ELEMENT-FREE EXTENSION OF SAID TAPE AND CORD, AND A CONTINUOUS LINE OF STITCHING WHICH HOLDS TOGETHER SAID SERIES OF LOOPS, CORD AND TAPE, SAID LINE OF STITCHING EXTENDING THROUGH SAID ELEMENT-FREE EXTENSION WHERE IT TIGHTLY BINDS THE CORD DIRECTLY TO THE TAPE. 